Sunday, February 22, 2009

Dredging Cagayan de Oro River will not solve floods, experts say

American Chronicle: Dredging the Cagayan River [in the Philippines] will not prevent further floods, a team of experts from the University of the Philippines said Thursday. The team from the National Institute of Geological Sciences (Nigs) of U.P. Diliman was headed by Prof. Fernando Siringan, Prof. Alfredo Mahar Lagmay and Prof. Emeritus Kelvin Rodolfo, also of the University of Illinois.

"Dredging the Cagayan River is not necessary," Siringan said in his luncheon presentation made to members and guests of the Rotary Club of Cagayan de Oro (Mother Club) held at a local hotel Thursday, Feb. 19. "It is costly, very short term and a recurring cost. It has very little effect in low areas and deepening an estuary only brings sea water inland, poisoning ground water and soils."

Because the central and business district of Cagayan de Oro is built on a delta or flood plain built by the gradual accretion of sediments, floods are part of its natural cycle. Large portions of the delta plain have elevations within two meters or lower of sea level and key infrastructure such as the Kagay-an Bridge rotunda are actually built on previous wetlands or recently abandoned river channels.

Thus, the city's central business district is influenced by tides, storm surges and tsunamis and with urbanization, floods have become a threat, Siringan said. Siringan had previously conducted studies of the Cagayan River in 1989-90, 1999 and 2001 for the Cagayan de Oro River Development Authority (CORDA) previously headed by Mayor Jaraula when he was still a city councilor.

… Instead of costly dredging, the U.P. team recommends a comprehensive package of measures to prevent a repeat of the two weekend floods last January which devastated Cagayan de Oro.

A 1720 map of the Cagayan River in the Philippines

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